[GreenKeys] Run teletype model 15/19 keyboard and printer on different circuits?

[Mike Douglas]

 I have found I had to go to 12v-15v across the keyboard to get reliable operation across a variety of machines. 5v may be OK for a given keyboard if its contacts are in good shape and show low resistance (< 1 ohm) when closed.

Directly running a relay coil with your keyboard isn't going to totally solve your arcing problem since the relay coil voltage will also build to the point it discharges via an arc across the keyboard contacts whenever a switch opens. There will be less energy stored in the relay coil than in a selector magnet coil, but you'll still get an arc. If you build a snubber for the relay coil, you have to be sure it still allows the relay to switch fast enough for reliable 45.5 baud operation.

Mike D

     On Tuesday, September 16, 2025 at 08:44:09 PM CDT, Windows XD <antech6586856 at gmail.com> wrote:  
 
 Dear all,
I was working on the teletype when I had an idea. I have already picked up a solid state relay capable of switching faster than the 45.45 baud needed for the teletype for something else I'm working on with the teletype, and I was wondering if it would be possible to run the keyboard on a 5vdc circuit wired to said solid state relay and have the keyboard run on 5vdc and the selector magnets at 120vdc. I can't think of any obvious problems with running the keyboard at this lower voltage, but I'd like to be sure.
I'm not sure I explained it super great so I've attached a schematic, although I'm not sure if it's any better than my explanation.
P.S. My keyboard has arcing problems with the contacts, will this modification coincidentally also fix that?______________________________________________________________
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